Load SHACL vocab into validation graph

Load the whole SHACL vocabulary from the web and add it to the generated
validation graph. This allows us to use additional information which can
not be found in `rdflib`, such as labels and descriptions of builtin
SHACL severities.

Author: zyzzyxdonta

src/software_card_policies/data_model.py

@@ -92,8 +92,6 @@ class Severity:
     comment: str
     level: SeverityLevel
 
-    # TODO: ``rdfs:label`` is ``None`` for SHACL's builtin severities. They exist in the
-    # SHACL source but the validator doesn't put them into the graph. Should we do it?
     def __str__(self):
         return self.label if self.label else str(self.level)
 
@@ -162,7 +160,7 @@ def read_rdf_resource(source: Path | str) -> Graph:
     graph = Graph()
     graph.parse(source)
     for prefix, iri in PREFIXES.items():
-        graph.bind(prefix, iri)
+        graph.bind(prefix, iri, replace=True)
     return graph
 
 
@@ -197,7 +195,8 @@ def _create_sc_scalar_parameter(
     return graph.value(parameter.uri, SC.parameterDefaultValue, None)
 
 
-# TODO: Is it safe to modify the graph while iterating over it?
+# TODO: Don't modify the graph while iterating over it! Collect new triples first, then
+# insert at the end!
 def parameterize_graph(graph: Graph, config_parameters: Dict[str, Any]) -> Graph:
     # iterate over all declared parameters of type `sc:Parameter`
     for parameter_ref in graph.subjects(RDF.type, SC.Parameter):
@@ -237,7 +236,6 @@ def parameterize_graph(graph: Graph, config_parameters: Dict[str, Any]) -> Graph
             graph.add((s, p, o))
 
         # remove all references to the parameter from the graph
-        # TODO: Keep all `(parameter.uri, None, None)` for debugging purposes?
         graph.remove((parameter.uri, None, None))
         graph.remove((None, None, parameter.uri))
 
@@ -254,9 +252,16 @@ def validate_graph(data_graph: Graph, shacl_graph: Graph) -> Tuple[bool, Graph]:
         do_owl_imports=True,
         js=True,
     )
-    # TODO: Is this required? Or are the bindings transferred from the data graph?
+
+    # Read the whole SHACL vocabulary into the graph so that we can use additional info
+    # such as labels and descriptions.
+    validation_graph.parse(SH._NS)
+
+    # Bind namespace prefixes for better readability. These _should_ already be bound;
+    # we're just making sure.
     for prefix, iri in PREFIXES.items():
-        validation_graph.bind(prefix, iri)
+        validation_graph.bind(prefix, iri, replace=True)
+
     return conforms, validation_graph